1. Field
The disclosure relates to a branching device for a transmission line that transmits information, and to a monitoring apparatus that monitors information transmissions using the branching device.
2. Description of the Related Art
The development of advanced information-based society has been accompanied by increased use of information processing and transmission in numerous different fields, with a wide range of different systems being adopted. In the vehicle control field as well, it has become common to use electronic control units in which microcomputers are applied to control the engine, transmission and the like. Information indicating the operation state of various different devices within an automobile that is used in electronic control is necessary for when the vehicle is running. In addition, the information is also useful for (a) carrying out regular vehicle inspections, and (b) dealing with problems if they occur.
Recently, there has been a trend in the North American automobile market toward making the provision of a vehicle diagnostic service using Controller Area Network communication (CAN communication) a legally required duty. CAN communication is a widely used transmission system for transmitting information between various control devices within a vehicle. The diagnostic service is a service that reads information from the vehicle in order to provide assistance for vehicle inspections, maintenance, and identifying the cause of any abnormality that occurs. In order to provide the diagnostic service, a transmission device, known as a service tool, is attached to the vehicle at a dealer's maintenance center, or the like. The information that is read includes (i) general data concerning the vehicle's operation state, like the vehicle speed, the engine revolution speed, and the gear shift stage, and (ii) a code number called a diagnosis code that systematically classifies an abnormality. The diagnostic service allows maintenance staff to rapidly determine the area of the vehicle and the specific nature of any abnormality that has occurred.